This invention relates to anti-tamper watthour meters and more particularly to an anti-tamper watthour meter having a voltage winding reversing arrangement including a gravity actuated switch assembly which prevents reverse meter operation upon installing the meter in an inverted position as an attempt to defraud electric utility billing. The invention further relates to an anti-tamper watthour meter which is operated in the inverted position at a faster than normal metering rate by a penalty metering arrangement including a gravity actuated magnetic member positioned adjacent a damping permanent magnet of the meter.
In electric utility metering, the use of induction type watthour meters installed at customers' meter sockets is well known. The electrical energy consumption indicated on a watthour meter register dial indicates a customer's electrical energy usage for purposes of billing by a utility company. In attempts to defraud the utility company, wire seals are broken and the meter is removed from its socket and reinstalled in an inverted position. This permits electric power service to be maintained through the inverted meter and causes the rotating metering movement to be rotated in the reverse direction. The watthour meter registers are driven reversely so that the register dial pointers are driven downscale indicating reduced consumption when actually electrical energy consumption is occurring. Reverse rotation of the watthour metering movement when it is mounted in the inverted position is caused by the reversing of the meter voltage winding connections across the line conductors causing a 180.degree. phase reversal of the voltage winding magnetic field.
It is known to prevent the aforementioned attempt to defraud the utility company by utilizing a detent assembly designated as Style No. 285 A 082 G02available from the Westinghouse Electric Corporation, Meter Division, Raleigh, N.C. which prevents the meter movement from rotating in the reverse direction. This prevents the down scale operation of the register when the meter is inverted. However, detent does not permit the meter to provide the normal billing indications. A further means of preventing defrauding of the utility companies is the use of a unidirectional register also available from the aforementioned meter manufacturer. The unidirectional register is always driven up scale regardless of the direction of rotation of the watthour metering movement. These unidirectional registers are more expensive, have additional parts and are more complex requiring increased driving torque by the metering movement, are more difficult to manufacture, and are sometimes found less reliable than the simpler standard meter registers.
Another solution to prevent tampering of watthour meters is disclosed in U.S. Pat. No. 3,915,112, issued Oct. 28, 1975, describing a meter position indicator. The patent describes a means for indicating on the front face of a meter cover that the meter has been inverted or rotated 180.degree.. This solution is helpful in detecting tampering of meters but does not prevent defrauding use of the watthour meter. In U.S. Pat. No. 2,546,693, issued July 9, 1947, an anti-tampering watthour meter is disclosed for preventing defrauding by short-circuiting the meter load or current windings. A relay is provided in the meter having two normally balanced coils and relay contacts which are connected to an auxiliary winding. When the meter is tampered with by providing the aforementioned short-circuited shunt, the auxiliary current winding is energized through the relay contacts to produce a faster than normal rotation of the metering movement. The last described anti-tampering electric meter undesirably includes additional relay coils and a winding and is directed to a type of metering tampering to which the present invention is not intended to prevent. Also, the meter is of the older bottom-connected type and not the socket-mounted type which is detachably mounted and to which the present invention pertains.